1. Field of the Invention
This invention generally relates to digital comparators and more specifically to optical comparators utilizing multicolor light emitting diodes.
2. Description of the Prior Art
A bistable device utilizing two electro-optical pairs connected in parallel is described in U.S. Pat. No. 2,997,596 issued on Aug. 22, 1961 to James F. Vize. Each pair includes serially connected monochromatic electroluminescent phosphor cell and photoconductor positioned in a radiation coupled relationship. The circuit exhibits two stable states and may be transferred to its other state by application of a light trigger signal.
A multicolor semiconductor lamp comprising a plurality of light emitting diodes for emitting light of respectively different colors is disclosed in U.S. Pat. No. 3,875,456 issued on Apr. 1, 1975 to Tsuyoshi Kano et al. The light emitting diodes are closely adjacent and covered by a layer of light scattering material to provide an appearance of a single light source.
Commercially well known digital comparator typically compares bit for bit two digital words and develops output digital signal indicating whether or not the two words are equal. The equality is usually determined by EXCLUSIVE-NOR circuits which individually compare equivalent bits in each word. If the compared digital words are not equal, the comparator is incapable of indicating the degree of similarity therebetween.
An optical comparator utilizing multicolor light emitting diodes for comparing digital signals is unknown.